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Probably the best-attended session of the American Association of Equine Practitioners (AAEP) annual convention, the Kester News Hour provides brief reports of studies that were too new or too brief to be included in the longer scientific sessions. Larry Bramlage, DVM, MS, Dipl. ACVS, the president-elect of the AAEP and a surgeon at the Rood and Riddle Equine Hospital in Lexington, Ky., and John Madigan, DVM, MS, Dipl. ACVIM, professor of Medicine and Epidemiology and section chief for Equine Medicine at the Veterinary Medical Teaching Hospital at the University of California, Davis, host this fun, high-energy session each year to kick off the convention.
This year, lameness studies were well represented, and other topics ran the gamut from infectious disease to antibiotic resistance, colic surgery complications, exercise-induced pulmonary hemorrhage, compounded medications, and much more.
West Nile Virus
Madigan reviewed that the West Nile virus (WNV) vaccine, and noted that practitioners are already familiar with it, but it is important to note that it takes a minium of two to three weeks after the second shot in the two-dose initial series for full immunity. Scientists presented field trials on the vaccine on Sept. 15 at an Office International des Epizooties meeting (see results in article #3903 at www.TheHorse.com). The study showed that horses vaccinated twice and challenged at 12 months with WNV via a needle challenge (virus injected and not using infected mosquitoes) were protected against the virus. Nine of 11 control horses (those which did not receive the vaccine) developed the viremia, while only one of 19 vaccinated horses had viremia.
Madigan said that protection should occur in nine of 10 horses if the vaccine prevents development of viremia as the study suggests. "Ten percent of WNV clinical cases have a history of being immunized--but most coming in haven't been immunized," he said.
Madigan explained that there seem to be a lot of differences between the WNV that was first detected in Africa and Europe in 1937 and the strain that has caused problems from 1999-2002 in the United States. "Old World" WNV didn't kill birds because the virus stays at low levels, whereas "New World" WNV sickens and kills birds by loading the bird up with virus. "The question is--do you think the virus from 1999 is becoming more virulent?" asked Madigan. He explained, "It was probably already more virulent and is simply marching along (and spreading throughout the continent)."
Researchers are finding out more and more about the virus, including that it can be spread by 37 different species of mosquitoes. They believe the current WNV strain originated in Israel and traveled in some way to the United States, where it reached a susceptible population of birds.
While WNV might seem formidable, Bramlage pointed out that the vaccine provides a good prevention mechanism. In all of the westernmost states, "it's going to establish itself there with the migration of birds. It would behoove everyone to be ready in those areas where it hasn't hit," said Bramlage.
They pointed out that it is important to remember that the horse is a dead-end host.
Magnetic Resonance Imaging in U.S. Equine Practice
According to Madigan, several U.S. clinics have sent letters of intent to companies in order to obtain magnetic resonance imaging (MRI) units, including the Virginia-Maryland Regional College of Veterinary Medicine, Texas A&M University, and Colorado State University.
"You see a lot of detail in the ligaments, soft tissue, bursa, and edema" with this equipment, he said. "It's going to be interesting to see how this new imaging is going to change (diagnostics)."
Bramlage said that his clinic was looking into the MRI technology as well. He said that MRI units are very new technology, and at some point in the future, "We may all have them."
EPM Consensus Statement Developed
Madigan reported that a panel for the American College of Veterinary Internal Medicine (ACVIM, www.acvim.org) met in 2002 and came up with a consensus statement on how a veterinarian should make a clinical diagnosis of equine protozoal myeloencephalitis (EPM). He read the statement: "A thorough physical and neurological exam are the primary and most important diagnostic processes for evaluation of horses suspected as having EPM. Then conclusive evidence of neurological abnormalities must be present and muscular disorders must be eliminated as the primary cause of lameness or gait abnormality."
Madigan said that diagnosing EPM is a continual puzzle. In order to consider EPM, first rule out lameness. Expect EPM, "If there is evidence of multifocal disease (pertaining to many locations). This is a parasite you'd expect to hit the nervous system at random. There is evidence of lesions affecting both the upper and lower motor neurons with associated muscle atrophy, incoordination and asymmetric signs," he said. Diagnosis is tricky and is going to largely based on clinical signs. Equine veterinarians are used to having to use clinical signs to make a disease diagnosis, an example being botulism, where a specific diagnostic test is not available and clinical signs are most important in the diagnosis.
Ancillary tests available for EPM diagnostics are the Western Blot test of either blood for spinal fluid for antibodies against the agent of EPM, Sarcocytis neurona. The evaluation of cerebrospinal fluid for intrathecal antibodies (antibodies produced in the nervous system) would be an indicator of active infection with Sarcocystis neurona. The rational for the testing of spinal fluid for antibodies to S. neurona was that if the horse was exposed to the agent, it would develop antibody in blood. If the organism worked its way into the nervous system, then antibody would be detected in the horse's spinal fluid. Recent work has now questioned that earlier thinking as well as revealing problems with the use of the Western Blot test.
One hindrance to accurate testing with the Western blot cerebrospinal fluid tests is blood contamination. "Small amounts of blood contamination during the CSF procedure produces leakage of antibody from serum into the sample and causes a false positive for Western Blot," said Madigan. Remember that the sample might look like crystal clear water, but you still could have red blood cell (blood) contamination.
In Western blot testing using spinal fluid, Madigan explained that you want to be as close to the lesions caused by S. neurona as possible. So, in a horse with rear limb signs, taking spinal fluid from the lumbosacral site might be more informative than a spinal tap just behind the head in the atlanto-occipital space.
He concluded that the Western blot test should not be used in normal horses as a screening test for the disease. But should we use the CSF for EPM testing at all? He said that the cytology and the biochemistry might be helpful, but you must determine if there has been blood cell contamination of spinal fluid, since any more than 10 red blood cells in a sample can cause a false positive.
Often the owner wants a test to confirm presence of EPM when the horse shows neurologic signs.
Madigan recalled a study in which horses were vaccinated with ova albumen to develop an antibody in the horse's blood. Even in clean CSF samples from the vaccinated horses, there was some antibody that found its way into the spinal fluid. In other words, "There was a dynamic equilibrium between antibody and CSF. So this raises into question whether the Western blot test of spinal fluid indicates an infection in the nervous system or if the antibody is there because the horse has blood antibodies from just being exposed to the agent.
"We're learning some things about the physiology of the nervous system," added Madigan. "Unfortunately, the only way a definitive diagnosis can be made is during a post-mortem exam." And unless the pathogen is found, results are often inconclusive.
Madigan cited a study published in the Journal of the American Veterinary Medical Association in 2002. Post-mortem examinations were completed on 234 horses in California. Of those horses, 65 had neurological issues prior to death, and only 12 of those 65 were positive for EPM upon necropsy and the sensitivity of the Western Blot test was only 44%. "The low specificity of the Western blot of CSF indicated that it is inappropriate to diagnose EPM on the basis of a positive Western blot on CSF alone because of the possibility of false positive results." said Madigan. "The Western blot tests' true sensitivity is unknown because even during a post mortem examination of the spinal cord, it is impractical to examine the entire spinal cord for the organism or inflammation."
Bramlage added, "If you have a horse with neurological disease--if you test him for EPM via a blood test and he's negative--then that is a pretty good predictor the horse has never been exposed to EPM and its unlikely the neurological signs are due to EPM. If the horse is turning out to be asymetric (in movement), ataxic, and multifocal, that's when you want to raise the ante and look into it further with spinal testing."
If a horse shows symmetric neurological signs, then you might want to consider that the horse is a wobbler.
Emergency Management
Fire departments and rescue personnel are fine-tuning their equine emergency skills. Madigan told about how the Felton Fire Department in California has been working with local equine veterinarians and trainers on handling horses in emergency situations, and that the team has regular training and practices.
In the event of a 911 call with an equine emergency, the fire department responds and a veterinarian is contacted simultaneously--both the veterinarian and emergency crews arrive on the scene and coordinate rescue or extraction.
"This is a great example of something that may spread and they're looking to make it a uniform thing throughout the fire departments in California," said Madigan. In addition to the veterinarian and fire department working together to extract horses from trailer accidents on the highway, there is the concern for those untrained in humane destruction of a horse. They are trying to steer the police away from putting down injured horses with a gunshot--shooting the horse between the eyes in an incorrect fashion because unless the horse anatomy is known, some attempts result in shooting out the frontal sinus. Having the veterinarian on the scene immediately ameliorates the situation.
Flair Nasal Strips and Airway Resistance
A recent Michigan State University study showed that Flair nasal strips tented the skin over the nasal valve, dilated that section of the nasal passage, and decreased airway resistance on inspiration during treadmill exercise (see article #3913 at www.TheHorse.com).
"The nasal strips probably decreased the amount of work required for respiratory muscles in horses during intense exercise, and may reduce the amount of energy needed," said Bramlage. "It hasn't been as effective in horses as it has in humans."
Navicular Syndrome in History
A veterinary paleontologist at the Idaho Museum of Natural History looked at navicular bones from horses that were anywhere from 10,000 to 3.5 million years old from four North American sites.
According to Madigan, 17% showed distal cones or "lollipop-shaped" voids in the navicular bone, suggesting that navicular disease has been endemic in the equine population for much of history, but that perhaps we aggravate it with our current uses of the horse.
Cross-Tying When Hauling
A recent study (Stull, C., et al. 2002) showed that cross-tying the horse during lengthy trailer rides increases the stresses as shown in serum cortisol levels and high white blood cell counts. The same horses were hauled loose in the trailer for the same amount of time, and there was less of an increase in serum cortisol.
Previous studies have shown that there is less contamination of the airway if the horse can eat off of the ground, and less problem in long transportation if the horse can lower its head to clear its airway.
Coat Clipping
Madigan reviewed a recent study in Sweden examining the physiological effects of winter clipping on equine athletes. After work, clipped horses had significantly lower problems with evaporation and heat loss, and required a shorter respiratory recovery period. Additionally, the clipped horses showed a decreased oxygen uptake with an increased workload, suggesting a more effective power output.
"Clipping appears to be not a bad thing," said Madigan. "It looks like there are some physical benefits (including) less stress on the thermoregulatory systems."
Muscle Cramps Associated with Ear Ticks
Madigan showed images of a horse with apparent neurological symptoms, and Bramlage was asked to help diagnose. After some discussion, it turned out that the horse had ear ticks (Otobius megnini) that somehow trigger a release of neurotoxins in the horse, causing muscle cramping. These horses can present with an atypical tying up, lameness, or stiffness with normal periods in between episodes. A unique characteristic of these cases is the rapid, painful hardening of the body muscle groups, which can be determined by by tapping the muscle and seeing a spontaneous contraction of the entire muscle group. Examine the ears in these cases for the ear ticks.
Evidence-Based Medicine
Madigan discussed the importance of improving treatment methods by integrating individual clinical experience with the best available external evidence from systematic research. "Ideas may start with individual efforts and topic reports ("How do I treat?"). Then, with time, cases accumulate and should be critically studied," he said.
EIPH in Racehorses
A study by Birks, et al., presented at the ICEEP (International Conference on Equine Exercise Physiology) meeting showed that Standardbred racehorses bleed from the airways as often as Thoroughbreds. Researchers examined 258 Thoroughbreds and 296 Standardbreds 45-80 minutes after the race and found that there was no significant relationship between severity of bleeding and finish performance.
Potomac Horse Fever
Madigan, an avid Potomac horse fever (PHF) researcher, reported that the name of the causative agent of the disease (once Ehrlichia risticii) has been changed to Neorickettsia risticii, based on its DNA relationship to a similar organism (see article # 3790 at www.TheHorse.com). The life cycle consists of water snails that release flukes when warm. The flukes survive in the water and infect larval insects by penetration, then develop into another fluke stage called a metacercariae. Researchers have found that at least 13 species of insects have a metacercariae phase containing the PHF agent, which persist into the adult stage of the insect so the PHF agent gets flown around and about pastures, barns, and other areas. Horses inadvertently eat the grown insects (for example, caddisflies) when they die and fall in the horse's feed or grass. He added that apparently N. risticii when in the metacercariae phase in the insect is acid-resistant, which is why the agent can be ingested and cause gastrointestinal infection.
Madigan said the real question in prevention of PHF in horses is figuring out how far these infected insects can fly. "Should you fence off creeks? No, that's not protective," he said. "I don't know how far from water the horse is safe, but we do know it's not water or snails, but the insects which emerge from rivers, creeks, or water ditches" that are causing the problem, he said.
IV or Oral Fluids for Hydration
Large intestine impactions are common in the horse, but what is better for hydrating these horses--intravenous (IV) or enteral (via the gastrointestinal tract) fluids?
A researcher at the Virginia-Maryland Regional College of Veterinary Medicine measured the consistency of fecal masses and determined that horses given enteral fluids held hydration longer than those given IV fluids. The horses on enteral fluids were more hydrated. "We don't want to forget this enteral route," he said, "It probably is another way to go."
Colic Risk Factors
Madigan also reviewed some risk factors for colic. Horses stabled for 24 hours a day are more at risk for colic than horses with a turnout schedule. Also, horses which:
* Are cribbers or windsuckers;
* Have traveled within the past 24 hours;
* Have had not had a recent ivermectin administration;
* Have experienced a recent change in their exercise level; and
* Have had their teeth checked fewer times.
Treatment of Gastric Ulcers with Gastrogard vs. Compounded Omeprazole
A UC Davis study showed that a compounded form of omeprazole was not as effective as the FDA-approved Gastrogard (see article #3868 at www.TheHorse.com). Researchers believe that the compounded form might have been broken down before reaching the small intestine (where it absorbs into the bloodstream), while GastroGard paste was formulated to protect the omeprazole from the acidity of the stomach--the pH of Gastrogard in the study was 8.4, whereas the compounded omeprazole was 3.4. Potentially, the already acidic nature of the suspension had eaten away at the omeprazole in the suspension.
"Is the Gastrogard findings the tip of the iceberg with regard to compounding products?" asked Madigan. "It raises some very important questions about what we give horses. We have to relay the information on variability of absorption and efficacy with the less expensive compounded products (to owners)," he added.
Glandular Ulcers
According to Madigan, a study from the International Colic Symposium done by Andrews, et. al., revealed that glandular ulcers are commonly missed when horses have their stomachs scoped using endoscopy. The examiner could find ulcers in the non-glandular portions of the stomach, but the ulcers in the lower portion of the stomach (glandular) were missed. The prevalence of glandular is high in stalled yearlings according to other studies done by Andrews. Out of 23 horses, only one horse was found to have glandular ulcers via endoscopic exam--yet six horses actually had the disorder identified on post mortem examination.
Research and Current Events
Finally, Madigan suggested that practitioners keep appraised of current research, and that they can search for recent research on specific topics at PubMed (www.PubMed.com). The service is free, but only abstracts are provided. But typically you can request specific papers from a nearby university library.
There is a movement to form a national animal identification initiative, which would establish a permanent equine identification method. "The concept is a good thing," said Bramlage, "but the problem is the implementation."
Bioterrorism is a threat to even the equine industry now, and Madigan addressed the topic. The bottom line is equine veterinarians need to be more alert to exotic equine diseases.
Non-Weight-Bearing Lameness
Bramlage discussed one study presented at the 2002 British Equine Veterinary Association (BEVA) convention that evaluated physical problems that could cause immediate non-weight-bearing lameness in the horse in the absence of ongoing disease processes. These included:
* Fracture;
* Luxation (dislocation of a joint);
* Synovial (relating to joint fluid) infection;
* Osteomyelitis (bone inflammation from infection with a pus-producing organism);
* Acute tendonitis/desmitis (tendon/ligament inflammation);
* Muscle injury;
* Nerve paralysis; and
* Diseases of the hoof (such as a progressive abscess).
Out of these conditions, four can occur with no apparent swelling, making them harder to identify and treat. These include fractures (if they are non-displaced), synovial cavity infection, tendonitis, and hoof disease (such as an abscess).
Risk Factors for Intestinal Surgery
Intestinal surgery is a complex procedure with many risks for further complications. Another study presented at the 2002 BEVA convention analyzed clinic records to discern the rate of occurrence of some of these factors. Following are the rates of incidence of each complication and risk factors associated with it.
* Diarrhea-19%-53% incidence, likelihood increased by lesions of the large intestine
* Post-op ileus (lack of gut motility)-20% incidence, likelihood increased with strangulated small intestine lesions and increased time of surgical procedure; likelihood decreased with pelvic flexure enterotomy (to evacuate gut contents)
* Herniation--16% incidence, risk increased by infection of incision.
* Adhesions--5-22% incidence, (probably higher, commented Bramlage), risk increased by resection of the small intestine.
* Laminitis--questionable incidence, risk possibly increased by proximal lesions, hemorrhagic reflux (reversed flow of ingesta through the intestine with bleeding), and increased body weight.
* Thrombophlebitis (vein inflammation, usually from infection)--undefined incidence, risk decreased by surgery.
* Disseminated intravascular coagulation (DIC, systemic blood clotting from endotoxins)--4% incidence; DIC decreased the likelihood of survival.
Fatal Fractures of the Distal Limb
Another study presented at the 2002 BEVA convention evaluated fatal distal limb fractures (109 cases) over two years of racing in the United Kingdom. It found that 80% of these fractures occurred in the forelimb, with 33% of these being condylar fractures). Roughly 72% of the horses with condylar fractures also fractured both sesamoid bones.
The study also noted that fatal distal limb fracture was more common:
* When racing over fences (compared to flat racing);
* When racing on all-weather surfaces;
* When the horse was reluctant to start;
* When the horse was moving up in the field during the race;
* When the horse was asked to accelerate;
* During the second half of a race; and
* When a horse had completed fewer fast training miles.
Musculoskeletal Injury in Racehorses in Training
Another 2002 BEVA meeting presentation evaluated severe musculoskeletal injury in United Kingdom racehorses in training. Researchers evaluated the records of 1,178 horses in 13 yards (stables), with a total of about 300,000 training days. Following are their findings.
* An incidence of 162 fractures; 149 were exercise-induced;
* 80% of these injuries occurred during training.
* The rate of fracture in training was determined to be 1.18 fractures per 100 horses per month, with 60% being stress fractures.
* Fracture of the spine or pelvis accounted for 16% of the fractures, with over 50% of fractures being of the forelimbs.
"Reluctance to train should be considered a sign (of a problem)," said Bramlage. "Horses really do like to run."
It was noted that in the 30-day period before fracture, risk of severe musculoskeletal injury increased when the number of high-speed furlongs run exceeded 40% of the number of medium-speed furlongs. Bramlage suggested that the results of this study along with the previously discussed study suggest that whatever work a horse does, "He has to adapt to it. The horses not adapted got injured." (For more information on bone adaptation to training, see the Milne Lecture at article #4066 at www.TheHorse.com).
Effect of Oral Phenylbutazone on Articular Cartilage
This study published in the American Journal of Veterinary Research used five control horses and six test horses to evaluate the effects of oral phenylbutazone (Bute, a non-steroidal anti-inflammatory medication) administration on articular cartilage. Cartilage from each horse was sampled at the beginning of the study, after two weeks of phenylbutazone administration twice daily, and again after two weeks off of the medication.
During joint disease, Bramlage said that the normal processes of cartilage breakdown and production slow down significantly, which is good. Phenylbutazone did not appear to harm the articular cartilage, with no significant difference between the samples from treated and untreated horses except for the samples taken after two weeks of relatively high phenylbutazone treatment (in terms of proteoglycan production). In fact, two weeks after phenylbutazone administration was stopped, the test horses' production of proteglycan was nearly back to normal, but their breakdown of proteoglycan was still low (which would result in a net gain of proteoglycan).
The researchers who conducted the study recommended that prolonged administration of phenylbutazone might not be the best thing for the joints, and that it should be used <I>judiciously<I>. Bramlage agreed that judicious use was key, and added, "Give Bute to the horse if he needs it; it doesn't hurt the diseased joints and probably helps."
More Phenylbutazone Effects
Another study on phenylbutazone published in the American Journal of Veterinary Research evaluated its effect on the right dorsal colon. The study found that it alters ion transport in the right dorsal colon and induces apoptosis (cell death). This area of the bowel is particularly susceptible to these effects, and the mucosa (mucous membrane lining) can be damaged as well. The question was posed as to whether these effects of phenylbutazone might be related to right dorsal colitis syndrome, but previous studies confirm this connection. Once that area of the bowel is affected, the horse can have an increased loss of protein from the gut and mild colic.
"The key is judicious use with a real emphasis on hydration," Bramlage said. "Some horses can only handle a little (phenylbutazone), while others can handle more."
Effects of Tongue Ties on the Airway
This study published in the American Journal of Veterinary Research used computed tomography to evaluate the effects of tongue ties (on five anesthetized horses). Nasopharyngeal dimensions and the position of the hyoid apparatus (the hyoid bones at the base of the tongue) were evaluated using three-dimensional images of each horse with and without the tongue tie. No significant difference between the images for each horse was found, and thus researchers concluded that no change in airway anatomy can be demonstrated; the physiology was not tested.
Pre-Exercise Stretching
Bramlage discussed an article from The Joint Letter in which a study of human military recruits evaluated the value of stretching in injury prevention. The conclusion of the study was that stretching did not prevent injury, although some of the subjects did report feeling better. Bramlage noted that warming up, as in racehorse warm-ups, might have more of an effect than stretching based on the studies.
Actinobacillus Resistance
Antibiotic resistance is a serious concern, and a study recently published in the Journal of the American Veterinary Medical Association discussed patterns of resistance discovered in various Actinobacillus species.
"Actinobacillus is becoming a much more important bacteria," commented Madigan.
Out of 1,604 surgeries studied, 1.43% (23 cases) had wound infections, 10 of which (43%) had Actinobacillus species in them. These isolates were all resistant to penicillin, bacitracin, and vancomycin; six were resistant to SMZ (sulfa/trimethaprim combinations). All were sensitive to gentamicin.
Bramlage discussed the antibiotic protocol at Rood and Riddle Equine Hospital, noting that Actinobacillus species are now commonly resistant to gentamicin. He suggested that different species might exhibit different resistance patterns in different areas based on common antibiotic practices.
He also discussed the question of whether prophylactic antibiotics should be used prior to surgery, noting that they are necessary for preventing respiratory issues, as a small number of horses develop pleuritis (inflammation of the pleura, or membrane lining the lungs) without them. Another note was that foals aborted from mares with mare reproductive loss syndrome (MRLS) had a high incidence of Actinobacillus isolates, indicating a high prevalence in all horse flora populations.
Equine Life Spans
Bramlage described a French study presented at BEVA in 2002 that reviewed the causes of mortality and age at death in older horses. The researchers found that the average equine life span there was 28 years plus or minus five years. Cardiovascular problems were the cause of death in 41% of the horses, locomotor problems (such as degenerative disease and fractures) accounted for 18%, and 11% died of colic.
Bramlage estimated a horse to human years ratio of 10:1 for juvenile horses (since horses reach full maturity relatively more quickly than humans), and 2.2:1 for adult horses.
AAEP Updates
Bramlage took a few minutes during the Kester News Hour to discuss the results of a recent survey of AAEP members and what AAEP is doing to serve its members' needs. Based on the survey, the number one concern of members is good continuing education (CE) and the second is that not enough people are interested in careers in equine veterinary practice.
As far as CE goes, the biggest CE event from AAEP is clearly the annual convention. Members have indicated that they want more interactive workshops, and this will be taken into consideration for next year's convention. Other CE events include the practice management meeting and resort symposiums; the Encore meeting, which was intended to provide information from the main convention at a different time and location to reach more members, has not reached its target numbers and will be replaced by the Focus program, which will be a special seminar to "focus" on one specific topic. In 2003, the topic will be reproduction. A time and location for the meeting was to be announced early in 2003.
Student interest in equine veterinary medicine has been declining lately, noted Bramlage, because many think that there isn't as much money in equine practice as in small animal practice and more hours are required. However, equine veterinarians make more than small animal veterinarians after about eight years of practice, according to a 1999 survey published in Veterinary Economics. It's just the starting salary that is lower. "We need to go to the schools and counteract the thought that equine practice pays less; after eight years it actually pays more but requires more hours," said Bramlage. "Also, the cost of living is often less where we practice than in urban areas where most of the high-paying small animal jobs are located."
Additionally, he commented that with the earlier "tracking" of many veterinary schools, in which students have to choose their initial species focus earlier than before, they are making these choices with less exposure to horses. "We haven't spent enough time with veterinary students," he commented; "We need to get to them early and often through mentor programs."
As for the gender of veterinary students, Bramlage reported that in the 2000-2001 year, 71% were female, compared to a 60% female population across all college students. The starting salaries of the female veterinarians were within $1,000 per year of their male classmates.
He then briefly discussed owner education via myHorseMatters.com, the AAEP's official web site for horse owners.
Equine Recombinant Growth Hormone and Wound Healing
This study published in Veterinary Surgery investigated the effects of equine recombinant growth hormone (ERGH) on second intention wound healing (healing of an open wound that isn't sutured, or stitched closed). Each of the study horses received a 2 x 2.5-cm wound over one fore and one hind cannon bone, and natural healing progress was recorded twice weekly. Then, each horse received the same wounds on the other fore and hind limb, and ERGH was administered systemically. There was no significant effect.
Another study on ERGH published in the same publication found that tendons affected with induced tendonitis became larger and weaker during healing than untreated tendons. Therefore, it appears to be contraindicated for tendon healing and is ineffective for wound healing.
Internet Education
Another The Joint Letter article discussed a survey that stated that 73 million U.S. residents seek answers to human health questions online, and 72% of them say you can believe all or most information you find online. The article went on to say that "most (human) musculoskeletal information online is of uncertain pedigree and dubious accuracy." Bramlage added that a scientific background is necessary to discern what online information is reliable.
Dorsal Displacement of the Soft Palate (DDSP)
This study evaluated horses' throats at rest and after high-speed exercise on a treadmill, and looked at the correlation between the two examinations. At rest, 80% of the 92 horses were normal, but 38 (41%) exhibited DDSP with no previous history of noisy respiration after exercise. The researchers concluded that endoscopic examination of horses for DDSP would be more accurate when conducted after exercise compared to examination at rest.
Treatment of the affected horses varied with the clinician, but 64% of the 45 horses which received surgical treatment improved their average earnings per start.
Tendinitis and Heel Wedges
A study published in the American Journal of Veterinary Research evaluated the effectiveness of heel wedges for treating induced superficial digital flexor (SDF) tendonitis, which is often followed by bowed tendons. Force plate data and tendon forces were calculated on lame and sound limbs before and after heel wedges were applied. The study found that tendonitis increased the stress on the SDF, while decreasing tension on the suspensory ligament and deep digital flexor tendon.
The same trends in tendon strain were noted in the opposite, sound limbs, which often become sore after taking the additional load from the lame leg, Bramlage noted. "A bowed tendon (normally affecting the SDF) is very commonly a secondary disease from overloading one limb when the other one is sore," he commented.
After raising the horse's heels with wedges, an increase in stress on the SDF was found. Thus, heel wedges are contraindicated for tendonitis.
Physician Career Satisfaction
Bramlage briefly discussed a The Joint Letter article that discussed various medical specialists' satisfaction with their careers. Overall, 59% of doctors in the survey said they were happy with their careers, down from 82% in 1996. Roughly 53% would not recommend the medical profession to younger people considering the field, and the least satisfied specialists were OB/GYN specialists, orthopedists, and internists. Pediatricians and geriatric specialists were on the high end of the satisfaction spectrum.
Acupuncture for Colic
Although acupuncture is touted by many as a reliever for colic pain, a study published in the American Journal of Veterinary Research countered that belief. Colic was induced in the study horses by inserting a balloon into the duodenum endoscopically (first part of the small intestine) and inflating it, which is a highly controllable and repeatable method. Neither electroacupuncture nor standard acupuncture relieved clinical signs of pain in the horses.
Intraosseus vs. Intravenous Antibiotic Levels in Joints
The last study Bramlage discussed evaluated the concentration of amikacin sulfate in the tibiotarsal joint when injected intravenously (IV) vs. intraosseously (into the bone). Although a human study found a greater level of regional perfusion of the antibiotic when it was injected intraosseously, the equine study found the reverse; the IV route resulted in higher regional perfusion. "Horses are horses and people are people," concluded Bramlage. "Use the veins."
Out of Time
Bramlage and Madigan often bring reports of more studies than can be covered even in the rapid-fire format of the Kester News Hour. Here are summaries of the research reports that had to be dropped in favor of the schedule.
Synovial Regeneration After Synovectomy
Three groups of 4 horses each were evaluated in this study published in Veterinary Surgery, which examined the effects of arthroscopic mechanical or CO2 laser synovectomy (removal of a portion of a joint's synovial membrane). Researchers found that regeneration of the villi (joint fluid-producing projections located on this membrane) did not occur; instead, the villi were replaced by scar tissue.
"You can't just remove all the soft tissue in your way without ill effects," warns Bramlage.
Ultrasonography for Bone Evaluation
After reviewing this study published in the American Journal of Veterinary Research, Bramlage states that while measurement of sound transmission through bone is possible, it is not yet practical for clinical use.
This year, lameness studies were well represented, and other topics ran the gamut from infectious disease to antibiotic resistance, colic surgery complications, exercise-induced pulmonary hemorrhage, compounded medications, and much more.
West Nile Virus
Madigan reviewed that the West Nile virus (WNV) vaccine, and noted that practitioners are already familiar with it, but it is important to note that it takes a minium of two to three weeks after the second shot in the two-dose initial series for full immunity. Scientists presented field trials on the vaccine on Sept. 15 at an Office International des Epizooties meeting (see results in article #3903 at www.TheHorse.com). The study showed that horses vaccinated twice and challenged at 12 months with WNV via a needle challenge (virus injected and not using infected mosquitoes) were protected against the virus. Nine of 11 control horses (those which did not receive the vaccine) developed the viremia, while only one of 19 vaccinated horses had viremia.
Madigan said that protection should occur in nine of 10 horses if the vaccine prevents development of viremia as the study suggests. "Ten percent of WNV clinical cases have a history of being immunized--but most coming in haven't been immunized," he said.
Madigan explained that there seem to be a lot of differences between the WNV that was first detected in Africa and Europe in 1937 and the strain that has caused problems from 1999-2002 in the United States. "Old World" WNV didn't kill birds because the virus stays at low levels, whereas "New World" WNV sickens and kills birds by loading the bird up with virus. "The question is--do you think the virus from 1999 is becoming more virulent?" asked Madigan. He explained, "It was probably already more virulent and is simply marching along (and spreading throughout the continent)."
Researchers are finding out more and more about the virus, including that it can be spread by 37 different species of mosquitoes. They believe the current WNV strain originated in Israel and traveled in some way to the United States, where it reached a susceptible population of birds.
While WNV might seem formidable, Bramlage pointed out that the vaccine provides a good prevention mechanism. In all of the westernmost states, "it's going to establish itself there with the migration of birds. It would behoove everyone to be ready in those areas where it hasn't hit," said Bramlage.
They pointed out that it is important to remember that the horse is a dead-end host.
Magnetic Resonance Imaging in U.S. Equine Practice
According to Madigan, several U.S. clinics have sent letters of intent to companies in order to obtain magnetic resonance imaging (MRI) units, including the Virginia-Maryland Regional College of Veterinary Medicine, Texas A&M University, and Colorado State University.
"You see a lot of detail in the ligaments, soft tissue, bursa, and edema" with this equipment, he said. "It's going to be interesting to see how this new imaging is going to change (diagnostics)."
Bramlage said that his clinic was looking into the MRI technology as well. He said that MRI units are very new technology, and at some point in the future, "We may all have them."
EPM Consensus Statement Developed
Madigan reported that a panel for the American College of Veterinary Internal Medicine (ACVIM, www.acvim.org) met in 2002 and came up with a consensus statement on how a veterinarian should make a clinical diagnosis of equine protozoal myeloencephalitis (EPM). He read the statement: "A thorough physical and neurological exam are the primary and most important diagnostic processes for evaluation of horses suspected as having EPM. Then conclusive evidence of neurological abnormalities must be present and muscular disorders must be eliminated as the primary cause of lameness or gait abnormality."
Madigan said that diagnosing EPM is a continual puzzle. In order to consider EPM, first rule out lameness. Expect EPM, "If there is evidence of multifocal disease (pertaining to many locations). This is a parasite you'd expect to hit the nervous system at random. There is evidence of lesions affecting both the upper and lower motor neurons with associated muscle atrophy, incoordination and asymmetric signs," he said. Diagnosis is tricky and is going to largely based on clinical signs. Equine veterinarians are used to having to use clinical signs to make a disease diagnosis, an example being botulism, where a specific diagnostic test is not available and clinical signs are most important in the diagnosis.
Ancillary tests available for EPM diagnostics are the Western Blot test of either blood for spinal fluid for antibodies against the agent of EPM, Sarcocytis neurona. The evaluation of cerebrospinal fluid for intrathecal antibodies (antibodies produced in the nervous system) would be an indicator of active infection with Sarcocystis neurona. The rational for the testing of spinal fluid for antibodies to S. neurona was that if the horse was exposed to the agent, it would develop antibody in blood. If the organism worked its way into the nervous system, then antibody would be detected in the horse's spinal fluid. Recent work has now questioned that earlier thinking as well as revealing problems with the use of the Western Blot test.
One hindrance to accurate testing with the Western blot cerebrospinal fluid tests is blood contamination. "Small amounts of blood contamination during the CSF procedure produces leakage of antibody from serum into the sample and causes a false positive for Western Blot," said Madigan. Remember that the sample might look like crystal clear water, but you still could have red blood cell (blood) contamination.
In Western blot testing using spinal fluid, Madigan explained that you want to be as close to the lesions caused by S. neurona as possible. So, in a horse with rear limb signs, taking spinal fluid from the lumbosacral site might be more informative than a spinal tap just behind the head in the atlanto-occipital space.
He concluded that the Western blot test should not be used in normal horses as a screening test for the disease. But should we use the CSF for EPM testing at all? He said that the cytology and the biochemistry might be helpful, but you must determine if there has been blood cell contamination of spinal fluid, since any more than 10 red blood cells in a sample can cause a false positive.
Often the owner wants a test to confirm presence of EPM when the horse shows neurologic signs.
Madigan recalled a study in which horses were vaccinated with ova albumen to develop an antibody in the horse's blood. Even in clean CSF samples from the vaccinated horses, there was some antibody that found its way into the spinal fluid. In other words, "There was a dynamic equilibrium between antibody and CSF. So this raises into question whether the Western blot test of spinal fluid indicates an infection in the nervous system or if the antibody is there because the horse has blood antibodies from just being exposed to the agent.
"We're learning some things about the physiology of the nervous system," added Madigan. "Unfortunately, the only way a definitive diagnosis can be made is during a post-mortem exam." And unless the pathogen is found, results are often inconclusive.
Madigan cited a study published in the Journal of the American Veterinary Medical Association in 2002. Post-mortem examinations were completed on 234 horses in California. Of those horses, 65 had neurological issues prior to death, and only 12 of those 65 were positive for EPM upon necropsy and the sensitivity of the Western Blot test was only 44%. "The low specificity of the Western blot of CSF indicated that it is inappropriate to diagnose EPM on the basis of a positive Western blot on CSF alone because of the possibility of false positive results." said Madigan. "The Western blot tests' true sensitivity is unknown because even during a post mortem examination of the spinal cord, it is impractical to examine the entire spinal cord for the organism or inflammation."
Bramlage added, "If you have a horse with neurological disease--if you test him for EPM via a blood test and he's negative--then that is a pretty good predictor the horse has never been exposed to EPM and its unlikely the neurological signs are due to EPM. If the horse is turning out to be asymetric (in movement), ataxic, and multifocal, that's when you want to raise the ante and look into it further with spinal testing."
If a horse shows symmetric neurological signs, then you might want to consider that the horse is a wobbler.
Emergency Management
Fire departments and rescue personnel are fine-tuning their equine emergency skills. Madigan told about how the Felton Fire Department in California has been working with local equine veterinarians and trainers on handling horses in emergency situations, and that the team has regular training and practices.
In the event of a 911 call with an equine emergency, the fire department responds and a veterinarian is contacted simultaneously--both the veterinarian and emergency crews arrive on the scene and coordinate rescue or extraction.
"This is a great example of something that may spread and they're looking to make it a uniform thing throughout the fire departments in California," said Madigan. In addition to the veterinarian and fire department working together to extract horses from trailer accidents on the highway, there is the concern for those untrained in humane destruction of a horse. They are trying to steer the police away from putting down injured horses with a gunshot--shooting the horse between the eyes in an incorrect fashion because unless the horse anatomy is known, some attempts result in shooting out the frontal sinus. Having the veterinarian on the scene immediately ameliorates the situation.
Flair Nasal Strips and Airway Resistance
A recent Michigan State University study showed that Flair nasal strips tented the skin over the nasal valve, dilated that section of the nasal passage, and decreased airway resistance on inspiration during treadmill exercise (see article #3913 at www.TheHorse.com).
"The nasal strips probably decreased the amount of work required for respiratory muscles in horses during intense exercise, and may reduce the amount of energy needed," said Bramlage. "It hasn't been as effective in horses as it has in humans."
Navicular Syndrome in History
A veterinary paleontologist at the Idaho Museum of Natural History looked at navicular bones from horses that were anywhere from 10,000 to 3.5 million years old from four North American sites.
According to Madigan, 17% showed distal cones or "lollipop-shaped" voids in the navicular bone, suggesting that navicular disease has been endemic in the equine population for much of history, but that perhaps we aggravate it with our current uses of the horse.
Cross-Tying When Hauling
A recent study (Stull, C., et al. 2002) showed that cross-tying the horse during lengthy trailer rides increases the stresses as shown in serum cortisol levels and high white blood cell counts. The same horses were hauled loose in the trailer for the same amount of time, and there was less of an increase in serum cortisol.
Previous studies have shown that there is less contamination of the airway if the horse can eat off of the ground, and less problem in long transportation if the horse can lower its head to clear its airway.
Coat Clipping
Madigan reviewed a recent study in Sweden examining the physiological effects of winter clipping on equine athletes. After work, clipped horses had significantly lower problems with evaporation and heat loss, and required a shorter respiratory recovery period. Additionally, the clipped horses showed a decreased oxygen uptake with an increased workload, suggesting a more effective power output.
"Clipping appears to be not a bad thing," said Madigan. "It looks like there are some physical benefits (including) less stress on the thermoregulatory systems."
Muscle Cramps Associated with Ear Ticks
Madigan showed images of a horse with apparent neurological symptoms, and Bramlage was asked to help diagnose. After some discussion, it turned out that the horse had ear ticks (Otobius megnini) that somehow trigger a release of neurotoxins in the horse, causing muscle cramping. These horses can present with an atypical tying up, lameness, or stiffness with normal periods in between episodes. A unique characteristic of these cases is the rapid, painful hardening of the body muscle groups, which can be determined by by tapping the muscle and seeing a spontaneous contraction of the entire muscle group. Examine the ears in these cases for the ear ticks.
Evidence-Based Medicine
Madigan discussed the importance of improving treatment methods by integrating individual clinical experience with the best available external evidence from systematic research. "Ideas may start with individual efforts and topic reports ("How do I treat?"). Then, with time, cases accumulate and should be critically studied," he said.
EIPH in Racehorses
A study by Birks, et al., presented at the ICEEP (International Conference on Equine Exercise Physiology) meeting showed that Standardbred racehorses bleed from the airways as often as Thoroughbreds. Researchers examined 258 Thoroughbreds and 296 Standardbreds 45-80 minutes after the race and found that there was no significant relationship between severity of bleeding and finish performance.
Potomac Horse Fever
Madigan, an avid Potomac horse fever (PHF) researcher, reported that the name of the causative agent of the disease (once Ehrlichia risticii) has been changed to Neorickettsia risticii, based on its DNA relationship to a similar organism (see article # 3790 at www.TheHorse.com). The life cycle consists of water snails that release flukes when warm. The flukes survive in the water and infect larval insects by penetration, then develop into another fluke stage called a metacercariae. Researchers have found that at least 13 species of insects have a metacercariae phase containing the PHF agent, which persist into the adult stage of the insect so the PHF agent gets flown around and about pastures, barns, and other areas. Horses inadvertently eat the grown insects (for example, caddisflies) when they die and fall in the horse's feed or grass. He added that apparently N. risticii when in the metacercariae phase in the insect is acid-resistant, which is why the agent can be ingested and cause gastrointestinal infection.
Madigan said the real question in prevention of PHF in horses is figuring out how far these infected insects can fly. "Should you fence off creeks? No, that's not protective," he said. "I don't know how far from water the horse is safe, but we do know it's not water or snails, but the insects which emerge from rivers, creeks, or water ditches" that are causing the problem, he said.
IV or Oral Fluids for Hydration
Large intestine impactions are common in the horse, but what is better for hydrating these horses--intravenous (IV) or enteral (via the gastrointestinal tract) fluids?
A researcher at the Virginia-Maryland Regional College of Veterinary Medicine measured the consistency of fecal masses and determined that horses given enteral fluids held hydration longer than those given IV fluids. The horses on enteral fluids were more hydrated. "We don't want to forget this enteral route," he said, "It probably is another way to go."
Colic Risk Factors
Madigan also reviewed some risk factors for colic. Horses stabled for 24 hours a day are more at risk for colic than horses with a turnout schedule. Also, horses which:
* Are cribbers or windsuckers;
* Have traveled within the past 24 hours;
* Have had not had a recent ivermectin administration;
* Have experienced a recent change in their exercise level; and
* Have had their teeth checked fewer times.
Treatment of Gastric Ulcers with Gastrogard vs. Compounded Omeprazole
A UC Davis study showed that a compounded form of omeprazole was not as effective as the FDA-approved Gastrogard (see article #3868 at www.TheHorse.com). Researchers believe that the compounded form might have been broken down before reaching the small intestine (where it absorbs into the bloodstream), while GastroGard paste was formulated to protect the omeprazole from the acidity of the stomach--the pH of Gastrogard in the study was 8.4, whereas the compounded omeprazole was 3.4. Potentially, the already acidic nature of the suspension had eaten away at the omeprazole in the suspension.
"Is the Gastrogard findings the tip of the iceberg with regard to compounding products?" asked Madigan. "It raises some very important questions about what we give horses. We have to relay the information on variability of absorption and efficacy with the less expensive compounded products (to owners)," he added.
Glandular Ulcers
According to Madigan, a study from the International Colic Symposium done by Andrews, et. al., revealed that glandular ulcers are commonly missed when horses have their stomachs scoped using endoscopy. The examiner could find ulcers in the non-glandular portions of the stomach, but the ulcers in the lower portion of the stomach (glandular) were missed. The prevalence of glandular is high in stalled yearlings according to other studies done by Andrews. Out of 23 horses, only one horse was found to have glandular ulcers via endoscopic exam--yet six horses actually had the disorder identified on post mortem examination.
Research and Current Events
Finally, Madigan suggested that practitioners keep appraised of current research, and that they can search for recent research on specific topics at PubMed (www.PubMed.com). The service is free, but only abstracts are provided. But typically you can request specific papers from a nearby university library.
There is a movement to form a national animal identification initiative, which would establish a permanent equine identification method. "The concept is a good thing," said Bramlage, "but the problem is the implementation."
Bioterrorism is a threat to even the equine industry now, and Madigan addressed the topic. The bottom line is equine veterinarians need to be more alert to exotic equine diseases.
Non-Weight-Bearing Lameness
Bramlage discussed one study presented at the 2002 British Equine Veterinary Association (BEVA) convention that evaluated physical problems that could cause immediate non-weight-bearing lameness in the horse in the absence of ongoing disease processes. These included:
* Fracture;
* Luxation (dislocation of a joint);
* Synovial (relating to joint fluid) infection;
* Osteomyelitis (bone inflammation from infection with a pus-producing organism);
* Acute tendonitis/desmitis (tendon/ligament inflammation);
* Muscle injury;
* Nerve paralysis; and
* Diseases of the hoof (such as a progressive abscess).
Out of these conditions, four can occur with no apparent swelling, making them harder to identify and treat. These include fractures (if they are non-displaced), synovial cavity infection, tendonitis, and hoof disease (such as an abscess).
Risk Factors for Intestinal Surgery
Intestinal surgery is a complex procedure with many risks for further complications. Another study presented at the 2002 BEVA convention analyzed clinic records to discern the rate of occurrence of some of these factors. Following are the rates of incidence of each complication and risk factors associated with it.
* Diarrhea-19%-53% incidence, likelihood increased by lesions of the large intestine
* Post-op ileus (lack of gut motility)-20% incidence, likelihood increased with strangulated small intestine lesions and increased time of surgical procedure; likelihood decreased with pelvic flexure enterotomy (to evacuate gut contents)
* Herniation--16% incidence, risk increased by infection of incision.
* Adhesions--5-22% incidence, (probably higher, commented Bramlage), risk increased by resection of the small intestine.
* Laminitis--questionable incidence, risk possibly increased by proximal lesions, hemorrhagic reflux (reversed flow of ingesta through the intestine with bleeding), and increased body weight.
* Thrombophlebitis (vein inflammation, usually from infection)--undefined incidence, risk decreased by surgery.
* Disseminated intravascular coagulation (DIC, systemic blood clotting from endotoxins)--4% incidence; DIC decreased the likelihood of survival.
Fatal Fractures of the Distal Limb
Another study presented at the 2002 BEVA convention evaluated fatal distal limb fractures (109 cases) over two years of racing in the United Kingdom. It found that 80% of these fractures occurred in the forelimb, with 33% of these being condylar fractures). Roughly 72% of the horses with condylar fractures also fractured both sesamoid bones.
The study also noted that fatal distal limb fracture was more common:
* When racing over fences (compared to flat racing);
* When racing on all-weather surfaces;
* When the horse was reluctant to start;
* When the horse was moving up in the field during the race;
* When the horse was asked to accelerate;
* During the second half of a race; and
* When a horse had completed fewer fast training miles.
Musculoskeletal Injury in Racehorses in Training
Another 2002 BEVA meeting presentation evaluated severe musculoskeletal injury in United Kingdom racehorses in training. Researchers evaluated the records of 1,178 horses in 13 yards (stables), with a total of about 300,000 training days. Following are their findings.
* An incidence of 162 fractures; 149 were exercise-induced;
* 80% of these injuries occurred during training.
* The rate of fracture in training was determined to be 1.18 fractures per 100 horses per month, with 60% being stress fractures.
* Fracture of the spine or pelvis accounted for 16% of the fractures, with over 50% of fractures being of the forelimbs.
"Reluctance to train should be considered a sign (of a problem)," said Bramlage. "Horses really do like to run."
It was noted that in the 30-day period before fracture, risk of severe musculoskeletal injury increased when the number of high-speed furlongs run exceeded 40% of the number of medium-speed furlongs. Bramlage suggested that the results of this study along with the previously discussed study suggest that whatever work a horse does, "He has to adapt to it. The horses not adapted got injured." (For more information on bone adaptation to training, see the Milne Lecture at article #4066 at www.TheHorse.com).
Effect of Oral Phenylbutazone on Articular Cartilage
This study published in the American Journal of Veterinary Research used five control horses and six test horses to evaluate the effects of oral phenylbutazone (Bute, a non-steroidal anti-inflammatory medication) administration on articular cartilage. Cartilage from each horse was sampled at the beginning of the study, after two weeks of phenylbutazone administration twice daily, and again after two weeks off of the medication.
During joint disease, Bramlage said that the normal processes of cartilage breakdown and production slow down significantly, which is good. Phenylbutazone did not appear to harm the articular cartilage, with no significant difference between the samples from treated and untreated horses except for the samples taken after two weeks of relatively high phenylbutazone treatment (in terms of proteoglycan production). In fact, two weeks after phenylbutazone administration was stopped, the test horses' production of proteglycan was nearly back to normal, but their breakdown of proteoglycan was still low (which would result in a net gain of proteoglycan).
The researchers who conducted the study recommended that prolonged administration of phenylbutazone might not be the best thing for the joints, and that it should be used <I>judiciously<I>. Bramlage agreed that judicious use was key, and added, "Give Bute to the horse if he needs it; it doesn't hurt the diseased joints and probably helps."
More Phenylbutazone Effects
Another study on phenylbutazone published in the American Journal of Veterinary Research evaluated its effect on the right dorsal colon. The study found that it alters ion transport in the right dorsal colon and induces apoptosis (cell death). This area of the bowel is particularly susceptible to these effects, and the mucosa (mucous membrane lining) can be damaged as well. The question was posed as to whether these effects of phenylbutazone might be related to right dorsal colitis syndrome, but previous studies confirm this connection. Once that area of the bowel is affected, the horse can have an increased loss of protein from the gut and mild colic.
"The key is judicious use with a real emphasis on hydration," Bramlage said. "Some horses can only handle a little (phenylbutazone), while others can handle more."
Effects of Tongue Ties on the Airway
This study published in the American Journal of Veterinary Research used computed tomography to evaluate the effects of tongue ties (on five anesthetized horses). Nasopharyngeal dimensions and the position of the hyoid apparatus (the hyoid bones at the base of the tongue) were evaluated using three-dimensional images of each horse with and without the tongue tie. No significant difference between the images for each horse was found, and thus researchers concluded that no change in airway anatomy can be demonstrated; the physiology was not tested.
Pre-Exercise Stretching
Bramlage discussed an article from The Joint Letter in which a study of human military recruits evaluated the value of stretching in injury prevention. The conclusion of the study was that stretching did not prevent injury, although some of the subjects did report feeling better. Bramlage noted that warming up, as in racehorse warm-ups, might have more of an effect than stretching based on the studies.
Actinobacillus Resistance
Antibiotic resistance is a serious concern, and a study recently published in the Journal of the American Veterinary Medical Association discussed patterns of resistance discovered in various Actinobacillus species.
"Actinobacillus is becoming a much more important bacteria," commented Madigan.
Out of 1,604 surgeries studied, 1.43% (23 cases) had wound infections, 10 of which (43%) had Actinobacillus species in them. These isolates were all resistant to penicillin, bacitracin, and vancomycin; six were resistant to SMZ (sulfa/trimethaprim combinations). All were sensitive to gentamicin.
Bramlage discussed the antibiotic protocol at Rood and Riddle Equine Hospital, noting that Actinobacillus species are now commonly resistant to gentamicin. He suggested that different species might exhibit different resistance patterns in different areas based on common antibiotic practices.
He also discussed the question of whether prophylactic antibiotics should be used prior to surgery, noting that they are necessary for preventing respiratory issues, as a small number of horses develop pleuritis (inflammation of the pleura, or membrane lining the lungs) without them. Another note was that foals aborted from mares with mare reproductive loss syndrome (MRLS) had a high incidence of Actinobacillus isolates, indicating a high prevalence in all horse flora populations.
Equine Life Spans
Bramlage described a French study presented at BEVA in 2002 that reviewed the causes of mortality and age at death in older horses. The researchers found that the average equine life span there was 28 years plus or minus five years. Cardiovascular problems were the cause of death in 41% of the horses, locomotor problems (such as degenerative disease and fractures) accounted for 18%, and 11% died of colic.
Bramlage estimated a horse to human years ratio of 10:1 for juvenile horses (since horses reach full maturity relatively more quickly than humans), and 2.2:1 for adult horses.
AAEP Updates
Bramlage took a few minutes during the Kester News Hour to discuss the results of a recent survey of AAEP members and what AAEP is doing to serve its members' needs. Based on the survey, the number one concern of members is good continuing education (CE) and the second is that not enough people are interested in careers in equine veterinary practice.
As far as CE goes, the biggest CE event from AAEP is clearly the annual convention. Members have indicated that they want more interactive workshops, and this will be taken into consideration for next year's convention. Other CE events include the practice management meeting and resort symposiums; the Encore meeting, which was intended to provide information from the main convention at a different time and location to reach more members, has not reached its target numbers and will be replaced by the Focus program, which will be a special seminar to "focus" on one specific topic. In 2003, the topic will be reproduction. A time and location for the meeting was to be announced early in 2003.
Student interest in equine veterinary medicine has been declining lately, noted Bramlage, because many think that there isn't as much money in equine practice as in small animal practice and more hours are required. However, equine veterinarians make more than small animal veterinarians after about eight years of practice, according to a 1999 survey published in Veterinary Economics. It's just the starting salary that is lower. "We need to go to the schools and counteract the thought that equine practice pays less; after eight years it actually pays more but requires more hours," said Bramlage. "Also, the cost of living is often less where we practice than in urban areas where most of the high-paying small animal jobs are located."
Additionally, he commented that with the earlier "tracking" of many veterinary schools, in which students have to choose their initial species focus earlier than before, they are making these choices with less exposure to horses. "We haven't spent enough time with veterinary students," he commented; "We need to get to them early and often through mentor programs."
As for the gender of veterinary students, Bramlage reported that in the 2000-2001 year, 71% were female, compared to a 60% female population across all college students. The starting salaries of the female veterinarians were within $1,000 per year of their male classmates.
He then briefly discussed owner education via myHorseMatters.com, the AAEP's official web site for horse owners.
Equine Recombinant Growth Hormone and Wound Healing
This study published in Veterinary Surgery investigated the effects of equine recombinant growth hormone (ERGH) on second intention wound healing (healing of an open wound that isn't sutured, or stitched closed). Each of the study horses received a 2 x 2.5-cm wound over one fore and one hind cannon bone, and natural healing progress was recorded twice weekly. Then, each horse received the same wounds on the other fore and hind limb, and ERGH was administered systemically. There was no significant effect.
Another study on ERGH published in the same publication found that tendons affected with induced tendonitis became larger and weaker during healing than untreated tendons. Therefore, it appears to be contraindicated for tendon healing and is ineffective for wound healing.
Internet Education
Another The Joint Letter article discussed a survey that stated that 73 million U.S. residents seek answers to human health questions online, and 72% of them say you can believe all or most information you find online. The article went on to say that "most (human) musculoskeletal information online is of uncertain pedigree and dubious accuracy." Bramlage added that a scientific background is necessary to discern what online information is reliable.
Dorsal Displacement of the Soft Palate (DDSP)
This study evaluated horses' throats at rest and after high-speed exercise on a treadmill, and looked at the correlation between the two examinations. At rest, 80% of the 92 horses were normal, but 38 (41%) exhibited DDSP with no previous history of noisy respiration after exercise. The researchers concluded that endoscopic examination of horses for DDSP would be more accurate when conducted after exercise compared to examination at rest.
Treatment of the affected horses varied with the clinician, but 64% of the 45 horses which received surgical treatment improved their average earnings per start.
Tendinitis and Heel Wedges
A study published in the American Journal of Veterinary Research evaluated the effectiveness of heel wedges for treating induced superficial digital flexor (SDF) tendonitis, which is often followed by bowed tendons. Force plate data and tendon forces were calculated on lame and sound limbs before and after heel wedges were applied. The study found that tendonitis increased the stress on the SDF, while decreasing tension on the suspensory ligament and deep digital flexor tendon.
The same trends in tendon strain were noted in the opposite, sound limbs, which often become sore after taking the additional load from the lame leg, Bramlage noted. "A bowed tendon (normally affecting the SDF) is very commonly a secondary disease from overloading one limb when the other one is sore," he commented.
After raising the horse's heels with wedges, an increase in stress on the SDF was found. Thus, heel wedges are contraindicated for tendonitis.
Physician Career Satisfaction
Bramlage briefly discussed a The Joint Letter article that discussed various medical specialists' satisfaction with their careers. Overall, 59% of doctors in the survey said they were happy with their careers, down from 82% in 1996. Roughly 53% would not recommend the medical profession to younger people considering the field, and the least satisfied specialists were OB/GYN specialists, orthopedists, and internists. Pediatricians and geriatric specialists were on the high end of the satisfaction spectrum.
Acupuncture for Colic
Although acupuncture is touted by many as a reliever for colic pain, a study published in the American Journal of Veterinary Research countered that belief. Colic was induced in the study horses by inserting a balloon into the duodenum endoscopically (first part of the small intestine) and inflating it, which is a highly controllable and repeatable method. Neither electroacupuncture nor standard acupuncture relieved clinical signs of pain in the horses.
Intraosseus vs. Intravenous Antibiotic Levels in Joints
The last study Bramlage discussed evaluated the concentration of amikacin sulfate in the tibiotarsal joint when injected intravenously (IV) vs. intraosseously (into the bone). Although a human study found a greater level of regional perfusion of the antibiotic when it was injected intraosseously, the equine study found the reverse; the IV route resulted in higher regional perfusion. "Horses are horses and people are people," concluded Bramlage. "Use the veins."
Out of Time
Bramlage and Madigan often bring reports of more studies than can be covered even in the rapid-fire format of the Kester News Hour. Here are summaries of the research reports that had to be dropped in favor of the schedule.
Synovial Regeneration After Synovectomy
Three groups of 4 horses each were evaluated in this study published in Veterinary Surgery, which examined the effects of arthroscopic mechanical or CO2 laser synovectomy (removal of a portion of a joint's synovial membrane). Researchers found that regeneration of the villi (joint fluid-producing projections located on this membrane) did not occur; instead, the villi were replaced by scar tissue.
"You can't just remove all the soft tissue in your way without ill effects," warns Bramlage.
Ultrasonography for Bone Evaluation
After reviewing this study published in the American Journal of Veterinary Research, Bramlage states that while measurement of sound transmission through bone is possible, it is not yet practical for clinical use.